There are many types of inhalers that can provide delivered metered doses. The majority of inhalers of this kind are designed to provide multiple doses. It is however known that inhalers of this kind can also be used to provide a single dose.
In situations where a metered dose is to be dispensed it is important that the inhaler always dispenses the exact dose. There is also a problem with inhalers of this kind if there is a tendency to allow unintentional additional dosing. Inhalers need to be small, compact, easy to use and yet not too expensive. The inhalers also need to satisfy safety criteria set down by appropriate standards.
It is these issues that have brought about the present invention.